Applications that include electronic means to provide a safety-related function typically require a high safety integrity level (“SIL”) to prevent accidental initiation of the safety-related function. For example, an airbag in an automobile requires a high SIL to prevent unwanted airbag inflation, which by itself presents its own safety-related issues for an occupant of the automobile as well as substantial cost for its replacement. A signal to initiate an airbag firing squib should be confirmed by at least two independent instances that detect a need for the actuator action. The resulting architecture is called a one out of two, which means that one out of two systems may fail without initiating a dangerous event.
In systems such as airbag squib firing systems, an electronic control unit (“ECU”) such as a microcontroller is generally employed to process signals from at least two independent acceleration sensors to initiate the actuator action. However, there are functions on an ECU such as a power supply biasing function that are shared by multiple devices on the ECU. If a shared power supply biasing function that supplies a subsystem A and a subsystem B on the ECU produces an overvoltage condition, both subsystems may fail at once, thereby compromising the independence of these subsystems. One solution is to employ multiple power supplies that provide power for independent functions on multiple chips.
Providing independent signal processing elements in a cost-effective manner for a safety-related application such as an airbag squib firing arrangement is a key success factor for such systems in the marketplace. Present system designs address this need with complex signal-processing arrangements with attendant cost. The design of an improved arrangement to provide independent signal processing paths would address an unresolved application need.